Disposable diaper with absorbent member

ABSTRACT

A disposable diaper is provided comprising a liquid permeable topsheet, a liquid impermeable backsheet, and a liquid retentive absorbent member interposed between the two sheets, wherein the disposable diaper has a product basis weight of 50 to 220 g/cm 2 , and a portion of the disposable diaper where the absorbent member is positioned has a portion having a rate of body fluid absorption of 3.0 g/sec or more and a portion having a saturated body fluid absorption of 75 g/100 cm 2  or more.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP00/02328 which has an Internationalfiling date of Apr. 10, 2000, which designated the United States ofAmerica and was published in English.

TECHNICAL FIELD

The present invention relates to disposable diapers which are light andcompact and easy to carry around even when bunched up in a package andwhich are excellent in leakproofness.

The present invention also relates to absorbent articles, such asdisposable diapers, which are light and yet has a moderate thickness tosecure an easy feeling while in use.

1. Background Art

Improvements have been added to the structure and materials ofdisposable diapers to provide compact packages convenient to carry.

However, packages containing several disposable diapers now on themarket are still fairly heavy, some exceeding 3 kg, and carrying apackage has been a considerable burden.

It is a conceivable solution for lightening a package of disposablediapers to decrease the number of disposable diapers per package, butsuch reduces distribution efficiency, incurring an increase of unitprice and increasing the frequency of consumer purchases.

Mere cutting down the absorbent material to reduce the weight ofindividual disposable diapers would result in frequent leaks, making thediapers useless.

If absorbent articles such as disposable diapers are made thinner tomake the package more compact, the absorbent article feels flimsy andmakes a user feel a fear of leakage. Japanese Patent Laid-Open No.212072/93 discloses a technique in which an ultrathin functionalabsorbent member is used while securing some thickness by a combined useof a bulk layer. According to this technique, it is possible to providean absorbent article which comprises an ultrathin absorbent member andyet gives easy feelings, but the package is not at all compact.

2. Disclosure of the Invention

Accordingly, a primary object of the present invention is to provide adisposable diaper which is light and compact and convenient to carryeven when a plurality of the disposable diapers are packaged togetherand also which is excellent in leakproofness.

A secondary object of the present invention is to provide an absorbentarticle which is reduced in thickness and made more compact in apackaged state and restores its thickness on being taken out of thepackage for use thereby to make a user feel at ease while in use andwhich has cushioning to provide a good fit to a wearer on putting on.

The primary object of the present invention is accomplished by providinga disposable diaper comprising a liquid permeable topsheet, a liquidimpermeable backsheet, and a liquid retentive absorbent memberinterposed between the two sheets, wherein the disposable diaper has aproduct basis weight of 50 to 220 g/m², and a portion of the disposablediaper where the absorbent member is disposed has a part having a rateof body fluid absorption of 3.0 g/sec or more and a part having asaturated body fluid absorption of 75 g/100 cm² or more (hereinafterreferred to as a first invention).

The primary object of the invention is also accomplished by providing adisposable diaper comprising a liquid permeable topsheet, a liquidimpermeable backsheet, and a liquid retentive absorbent memberinterposed between the two sheets, wherein the disposable diaper has acrotch portion, and the crotch portion has a product basis weight of 100to 450 g/m², a rate of body fluid absorption of 3.0 g/sec or more, and asaturated body fluid absorption of 60 g/100 cm² or more (hereinafterreferred to as a second invention).

The primary object of the invention is also accomplished by providing adisposable diaper comprising a liquid permeable topsheet, a liquidimpermeable backsheet, and a liquid retentive absorbent memberinterposed between the two sheets, wherein the absorbent member containsa superabsorbent polymer A having a rate of absorption of 8 g/30 sec/0.3g or more measured by the DW method and a superabsorbent polymer Bhaving a rate of absorption of 5 g/30 sec/0.3 g or less measured by theDW method at a polymer A/polymer B weight ratio of 90/10 to 10/90 andhas a fluff pulp content of 0 to 30% by weight (hereinafter referred toas a third invention).

The secondary object of the present invention is accomplished byproviding an absorbent article comprising a liquid permeable topsheet, aliquid impermeable backsheet, and a liquid retentive absorbent memberinterposed between the two sheets, wherein the absorbent member has afluff pulp content of 0 to 30% by weight, and the thickness of theabsorbent article under a load of 180 gf/cm² and the thickness of theabsorbent article after unloading are such that the latter thickness is1.3 times or greater the former thickness (hereinafter referred to as aforth invention).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a disposable diaper as an embodiment ofthe present invention.

FIG. 2 is a schematic cross section of FIG. 1 taken along line X—X.

FIG. 3 is a schematic cross section of FIG. 1 taken along line Y—Y.

FIG. 4 is a schematic longitudinal section of FIG. 1 taken alone lineZ—Z.

FIG. 5 is a schematic view of the disposable diaper of FIG. 1 in itsflatly unfolded state, showing the position of the crotch portion of thediaper.

FIG. 6 is an illustration showing the method of evaluating absorbingperformance (maximum absorption) of a disposable diaper.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described hereunder with reference to thepreferred embodiments in the practice.

A disposable diaper according to a first embodiment of the presentinvention, which is one of the embodiments of the first invention, isexplained.

As shown in FIGS. 1 through 4, the disposable diaper of the firstembodiment has a liquid permeable topsheet 2, a liquid impermeablebacksheet 3, and a liquid retentive absorbent member 4 that isinterposed between the sheets 2 and 3. Fastening tapes 11 for fasteningare provided at both lateral edges B1 and B2 of the rear waist portion Bthat is positioned at the back side of a wearer. The disposable diaperof this embodiment is of so-called unfolded type.

In detail, the disposable diaper 1 of this embodiment has the absorbentmember 4, the backsheet 3 of substantially the same size as theabsorbent member 4, and the topsheet 2 which is arranged to cover thesurface and the sides of the absorbent member 4 as shown in FIGS. 1 to4. An outer nonwoven fabric layer 5 is arranged on the back side of thebacksheet 3. Water repellent nonwoven fabric 61 is provided on thetopsheet 2 on the side of the lateral side portions of the absorbentmember 4, with which to form upstanding gathers 6. The outer nonwovenfabric layer 5 and the water repellent nonwoven fabric 61 both extendfrom each lateral edge of the absorbent member 4 and fixed together,with leg elastic members 71 being held therebetween to form leg gathers7 on each lateral side. The free end 62 of the water repellent nonwovenfabric 61 is provided with an elastic member 63 to form upstandinggathers 6.

The outer nonwoven fabric layer 5 and the topsheet 2 extend from thelongitudinal edges of the disposable diaper 1 to form a pair of waistportions 8. Each waist portion 8 is provided with a waist elastic member81 having a band form, the elastic member 81 being fixedly sandwiched inbetween the topsheet 2 and the outer nonwoven fabric layer 5.

The absorbent member 4 is composed of nonwoven fabric 41 holding anabsorbent polymer 42 in the interstices among its constituent fibers andsupporting paper 43 wrapping the nonwoven fabric 41. Underneath theabsorbent member 4 is provided an uneven sheet 44 having compressiverecovery properties.

The outer nonwoven fabric layer 5 has on the front waist portion Athereof a landing tape 51 on which the fastening tapes 11 are to befixed.

The above-described basic structure of the disposable diaper 1 is commonto the other disposable diapers according to the embodiments of thesecond to fourth inventions hereinafter described.

The disposable diaper according to the first embodiment has a productbasis weight of 50 to 220 g/m², preferably 100 to 200 g/m², and itsportion where the absorbent member is disposed has a part having a rateof body fluid absorption of 3.0 g/sec or more, preferably 3.5 g/sec ormore, and a part having a saturated body fluid absorption of 75 g/100cm² or more, preferably 80 g/100 cm² or more.

The expression “the portion (of the disposable diaper) where theabsorbent member is disposed” is intended to mean the portion occupiedby the absorbent member when the disposable diaper is flatly unfoldedand seen in its plan view.

The “product basis weight”, “rate of body fluid absorption” and“saturated body fluid absorption” are measured as follows.

Product basis weight:

A disposable diaper is unfolded flatly, and the area (m²) in this stateis measured. The weight (g) of the disposable diaper divided by the areagives the product basis weight (g/m²). In this calculation, the area ofthe fastening tapes is not included in the product area. In case wherethe disposable diaper is of pants type, the joint parts between thelateral edges of the rear waist portion and the lateral edges of thefront waist portion are separated apart and unfolded flatly, and theproduct area is measured in this state.

Rate of Body Fluid Absorption

Test pieces of 100 mm by 100 mm are cut out from arbitrary sites of adisposable diaper where the absorbent member is disposed. In case wherethe width of the absorbent member is narrower than 100 mm, the width ofthe absorbent member is to be the width of the test piece. Each of theresulting test pieces is placed on a horizontal mount with its topsheetup. An acrylic resin cylinder having an inner diameter of 50 mm isvertically put on the central portion of the test piece, and 50 g ofphysiological saline is poured into the cylinder all at once. The timerequired for the physiological saline to soak into the test piece and todisappear from the topsheet is measured, and the amount (g) ofphysiological saline absorbed per second during the period from additionof physiological saline to disappearance is calculated to obtain therate of body fluid absorption (g/sec). The expression “the portion ofthe disposable diaper where the absorbent member is disposed has a parthaving a rate of body fluid absorption of 3.0 g/sec or more” is intendedto mean that one or more of the test pieces cut out from different siteshave a rate of body fluid absorption of 3.0 g/sec or more.

Saturated Body Fluid Absorption

Test pieces of 100 mm by 100 mm are cut out from arbitrary sites of adisposable diaper where the absorbent member is disposed. In case wherethe width of the absorbent member is narrower than 100 mm, the width ofthe absorbent member is to be the width of the test piece. Each of theresulting test pieces is put in a 150 mm by 150 mm nylon mesh (250 mesh)bag, and the bag is immersed in physiological saline for 1 minute andallowed to drain for 5 minutes. From the weight (g) after drainage, theweight (g) before immersion, and the area (cm²) of the test piece iscalculated the absorption (g) of physiological saline per 100 cm², whichis taken as a saturated body fluid absorption (g/100 m²). The expression“the portion of the disposable diaper where the absorbent member isdisposed has a part having a saturated body fluid absorption of 75 g/100cm² or more” is intended to mean that one or more of the test pieces cutout from different sites have a saturated body fluid absorption of 75g/100 cm² or more.

If the product basis weight of a disposable diaper is less than 50 g/m²,which is preferred for lightness and compactness, the diaper easilyleaks.

If the portion where an absorbent member is disposed has no part havinga rate of body fluid absorption of 3.0 g/sec or more, the diaper easilyleaks particularly when a considerable amount of urine is discharged ina short time.

If the portion where an absorbent member is disposed has no part havinga saturated body fluid absorption of 75 g/100 cm² or more, the diaperleaks easily where worn for a long time.

In order to secure high resistance to leakage of urine in whichever casewhere urine rushes out or where much urine is discharged over a longtime, it is preferred that both a part having a rate of body fluidabsorption of 3.0 g/sec or more (hereinafter referred to as a high-rateabsorbing part) and a part having a saturated body fluid absorption of75 g/100 cm² or more (hereinafter referred to as high-absorption part)be positioned in a urination point portion that corresponds to awearer's urination point. The term “urination point portion” as usedherein denotes the portion containing the urination point of the diaperwhile worn and its periphery. The high-absorption part and the high-rateabsorbing part may be the same part or different parts or overlap witheach other.

A disposable diaper according to a second embodiment of the presentinvention, which is one of the embodiments of the second invention, isexplained. The disposable diaper of the second embodiment is basicallythe same as the first embodiment in constitution so that the explanationgiven above with regard to the basic constitution applies to the secondembodiment.

The crotch portion of the disposable diaper according to the secondembodiment has a product basis weight of 100 to 450 g/m² (preferably 200to 400 g/m²), a rate of body fluid absorption of 3.0 g/sec or more(preferably 3.5 g/sec or more), and a saturated body fluid absorption of60 g/100 cm or more (preferably 75 g/100 cm² or more).

The term “crotch portion” as used herein designates the portion of thedisposable diaper which corresponds to the crotch of a wearer whileworn. More definitely, it is the shaded portion of FIG. 5, i.e., theportion in which the absorbent member 4 is disposed and which is betweena pair of leg portions 9 corresponding to the periphery of wearer's legsand having an arch shape in the plan view.

The “product basis weight”, “rate of body fluid absorption” and“saturated body fluid absorption” of the crotch portion are measured asfollows.

Product Basis Weight

A disposable diaper is unfolded flatly, and a 100 mm by 100 mm testpiece is cut out of the crotch portion. In case where the width of theabsorbent member is narrower than 100 mm, the width of the absorbentmember is to be the width of the test piece. Division of the weight (g)of the test piece by the area (m²) of the test piece gives the productbasis weight (g/m). In case where the disposable diaper is of pantstype, the joint parts between the lateral edges of the rear waistportion and the lateral edges of the front waist portion are separatedapart, the diaper is unfolded flatly, and a test piece is cut out.

Rate of Body Fluid Absorption

A 100 mm by 100 mm test piece is cut out in the same manner as in themeasurement of the product basis weight of the crotch portion. The rateof body fluid absorption is measured in the same manner as for the rateof body fluid absorption of the portion where the absorbent member isdisposed as described as for the first embodiment, except for using theabove prepared test piece.

Saturated Body Fluid Absorption

A 100 mm by 100 mm test piece is cut out in the same manner as in themeasurement of the product basis weight of the crotch portion. Thesaturated body fluid absorption is measured in the same manner as forthe saturated body fluid absorption of the portion where the absorbentmember is disposed as described with respect to the first embodiment,except for using the above prepared test piece.

If the crotch portion has a product basis weight less than 100 g/m²,which is preferred for lightness and compactness, the diaper easilyleaks. If the crotch portion has a product basis weight exceeding 450g/m2, it is difficult to obtain light and compact disposable diapers.

If the crotch portion has a rate of body fluid absorption less than 3.0g/sec, the diaper easily leaks particularly when a considerable amountof urine is discharged in a short time.

If the crotch portion has a saturated body fluid absorption less than 60g/100 cm², the diaper leaks easily where worn for a long time.

In order to secure high resistance to leakage of urine in whichever casewhere urine rushes out or where much urine is discharged over a longtime, it is preferred that the urination point portion, whichcorresponds to a wearer's urination point, has a rate of absorption of3.0 g/sec or more and a saturated absorption of 60 g/100 cm² or more.

The product basis weight, rate of body fluid absorption, and saturatedbody fluid absorption in the first invention can be achieved by reducingthe content of fluff pulp in the absorbent member 4 while retaining ahigh absorption rate and a high saturated absorption by use of apolymer.

Similarly, the product basis weight, rate of body fluid absorption, andsaturated body fluid absorption of the crotch portion in the secondinvention can be accomplished by reducing the content of fluff pulp inthe absorbent member 4 while retaining a high absorption rate and a highsaturated absorption by use of a polymer.

An absorbent member is made up mainly of an absorbent polymer, a fiberaggregate, and supporting paper wrapping the absorbent polymer and thefiber aggregate. In the first and second embodiments nonwoven fabric 41having an absorbent polymer 42 held in the fiber interstices thereof iswrapped in supporting paper 43.

The absorbent polymer which can be used in the absorbent member includesconventional known polymers, such as sodium polyacrylate, acrylicacid-vinyl alcohol copolymers, crosslinked sodium polyacrylate,starch-acrylic acid graft copolymers, isobutylene-maleic anhydridecopolymers and saponification products thereof, and polyaspartic acid.It is particularly preferred to use a combination of a superabsorbentpolymer A having a rate of absorption of 8 g/30 sec/0.3 g or more asmeasured by the DW method and a superabsorbent polymer B having a rateof absorption of 5 g/30 sec/0.3 g or less as measured by the DW methodat a polymer A/polymer B weight ratio of 90/10 to 10/90, with which itis feasible to greatly reduce the fluff pulp compared with ordinarydisposable diapers while retaining a high absorption rate and a highsaturated absorption.

The absorbent member 4 preferably has a fluff pulp content of from 0 upto 30% by weight for easily making the product basis weight of thediaper 50 to 220 g/m² and for easily making the product basis weight ofthe crotch portion 100 to 450 g/m². The fluff pulp content can be 0%.

The term “rate of absorption by the DW method (g/30 sec/0.3 g)” meansthe value of absorption obtained by a method using an apparatusgenerally known for carrying out the DW method (demand wettabilitytester), in which, with the liquid levels of physiological saline beingequal, 0.3 g of a superabsorbent polymer is scattered on a mount(diameter: 70 mm; No. 1 glass filter having placed thereon No. 2 filterpaper), and the water absorption after 30 seconds is gauged by readingthe scale on the buret indicating a drop of the liquid level ofphysiological saline (the water absorption at the time of scattering thepolymer is taken zero).

The fiber aggregate used in the absorbent member includes aggregates offluff pulp; hydrophilic fibers such as rayon fiber, cotton and celluloseacetate; polyolefin fibers, such as polyethylene (PE) and polypropylene(PP); polycondensation fibers, such as polyester and polyamide; andpolymers of vinyl monomers such as vinyl chloride and vinyl acetate.These fibers can be used either individually or as conjugate fibershaving two or more of them in the form of a laminate or a core/sheathstructure. Those which are hydrophobic can be made hydrophilic bytreating with a lubricant, etc. Where fiber having heat fusibility isused, the fiber aggregate may be fabricated into nonwoven fabric by heattreatment and the like, which will improve the strength of the absorbentmember.

Any supporting paper generally used in disposable diapers can be usedwith no particular restriction. The uneven sheet 44 may be omitted

Constituted as described above, the disposable diapers according to thefirst and second embodiments are light and compact and thereforeconvenient to carry even when bunched up in a package in which aplurality of the disposable diapers are stacked and compressed. Inaddition, they have high leakproofness, effectively preventing leakageof urine either in case where urine rushes out or in case where muchurine is discharged over a long time.

A disposable diaper according to a third embodiment of the presentinvention, which is one of the embodiments of the third invention, isexplained. The disposable diaper of the third embodiment is basicallythe same as the first embodiment in constitution so that the explanationgiven above with regard to the basic constitution of the firstembodiment applies to the third embodiment.

The absorbent member 4 of the disposable diaper according to the thirdembodiment contains a superabsorbent polymer A having a rate ofabsorption of 8 g/30 sec/0.3 g or more measured by the DW method and asuperabsorbent polymer B having a rate of absorption of 5 g/30 sec/0.3 gor less measured by the DW method at a polymer A/polymer B weight ratioof 90/10 to 10/90, preferably 80/20 to 20/80, and has a fluff pulpcontent of 0 to 30% by weight, preferably 0 to 20% by weight.

If the weight ratio of superabsorbent polymer A to superabsorbentpolymer B (A/B) exceeds 90/10, the discharged urine will be fixed in thesuperabsorbent polymers without diffusing in the absorbent member sothat the absorbent member cannot be made full use of, resulting inreduced absorbing performance. On the other hand, if the superabsorbentpolymers A/B weight ratio is less than 10/90, it is difficult to reducefluff pulp, making it difficult to render the disposable diaper lightand compact.

Various superabsorbent polymers well-known in the art, such as theabove-described superabsorbent polymers, can be used. In the thirdinvention, in particular, those having a rate of absorption of 8 g/30sec/0.3 g or more by the DW method and those having a rate of absorptionof 5 g/30 sec/0.3 g or less by the DW method are selected from among theknown superabsorbent polymers and combined at the above-specified weightratio.

By the combined use of the superabsorbent polymers A and B at thespecific ratio, it is feasible to retain a high rate of absorption and ahigh saturated absorption with a greatly reduced fluff pulp content.

The superabsorbent polymer B preferably has a rate of absorption of 0.5g/30 sec/0.3 g or more by the DW method. It is preferred for thesuperabsorbent polymer A to have as high a rate of absorption by the DWmethod as possible.

The total content of the superabsorbent polymer A and the superabsorbentpolymer B in the absorbent member 4 is preferably 50% by weight or more,more preferably 50 to 99% by weight, particularly 60 to 95% by weight.

For obtaining disposable diapers having a high rate of absorption and ahigh saturated absorption, it is preferred that the superabsorbentpolymers A and B be present in the absorbent member in a mutually mixedstate.

In the third invention, the absorbent member 4 has a fluff pulp contentof 0 to 30% by weight. If the fluff pulp content in the absorbent memberis more than 30% by weight, it is difficult to make the disposablediapers significantly lighter and more compact. The fluff pulp contentcan be 0%.

The absorbent member of the third invention can be made up mainly of forexample, an absorbent polymer, a fiber aggregate, and supporting paperin which the former two are wrapped. The relationship between theabsorbent polymer and the fiber aggregate is not particularlyrestricted. In the third embodiment, a mixture of the aforementionedsuperabsorbent polymers A and B is used as the absorbent polymer 42 asbeing held in the fiber interstices of the nonwoven fabric 41 as thefiber aggregate.

The fiber aggregate and the supporting paper can be the same as thoseused in the first and second embodiments.

A disposable diaper according to a fourth embodiment of the presentinvention, which is one of the embodiments of the fourth invention, isthen explained. The disposable diaper of the fourth embodiment isbasically the same as the first embodiment in constitution so that theexplanation given above with regard to the basic constitution of thefirst embodiment applies to the fourth embodiment.

The absorbent member of the disposable diaper according to the fourthembodiment has a fluff pulp content of 30% by weight or smaller,preferably 0 to 20% by weight. The thickness of the absorbent articleunder a load of 180 gf/cm² and the thickness of the absorbent articleafter unloading are such that the latter is 1.3 times or greater theformer, preferably 1.5 to 3 times (this ratio will hereinafter bereferred to as a thickness ratio).

If the fluff pulp content exceeds 30% by weight, the package is notcompact. The smaller the fluff pulp content, the preferred for makingthe absorbent member thinner. This invention includes an embodiment inwhich no fluff pulp is used, i.e., the fluff pulp content is 0% byweight.

With the above thickness ratio is smaller than 1.3, an easy feelingcannot be secured on use.

The thickness under load and the thickness after unloading are measuredaccording to the following methods.

The absorbent article is unfolded flatly, and a test piece having awidth of 100 mm along the lateral direction and a length of 100 mm alongthe longitudinal direction of the article is cut out, the center of thetest piece agreeing with the intersection between a line longitudinallydividing the article into two equal pieces and a line laterally dividingthe article into two equal pieces. Where the longitudinal or lateralsize of the absorbent article is smaller than 100 mm, the size of theabsorbent article is to be the size of the test piece.

The test piece is placed on a horizontal mount and allowed to stand for24 hours with no load applied. Then, an acrylic resin plate and a weightis put thereon, and the test piece is further allowed to stand under theload for 24 hours. The weight and size of the weight is decided so as togive the test piece a total load of 180 gf/cm² together with the acrylicresin plate. The acrylic resin plate used was 100 mm wide, 100 mm long,and 5 mm thick.

After 24 hour loading, the thickness of each corner of the test pieceunder load is measured (measurement 1) to obtain an average thickness ofthe four corners, which is taken as a thickness under a load of 180gf/cm².

The weight and the acrylic resin plate are removed, and the unloadedtest piece is left to stand. After 30 minute standing, an acrylic resinplate and a weight giving a total load of 1 gf/cm² is placed thereon toflatten the test piece because any warpage or distortion of the testpiece would prevent accurate thickness measurement. The weight and sizeof the weight used is decided so as to give the test piece a total loadof 1 gf/cm² together with the acrylic resin plate. The acrylic resinplate used was 100 mm wide, 100 mm long, and 5 mm thick. Immediatelyafter putting the acrylic resin plate and the weight, the thickness ofthe test piece is measured in the same manner as in the measurement 1,and the average of the measured values is taken as a non-load thickness.

The above-specified thickness ratio can be obtained by, for example,using a cushioning material. In this particular embodiment, the unevensheet 44 is used as a cushioning material.

The above-described cushioning material preferably has a compressiverecovery of 60% or more, particularly 70 to 100%. The compressiverecovery is measured as follows.

Before measurement, a cushioning material is allowed to stand for 24hours to remove any strain that may have been imposed. The strain-freethickness (thickness before compressing the cushioning material) istaken as “a” mm, and the thickness after compressing under a pressure of180 g/cm² for 24 hours followed by removing pressure and allowing it tostand for 30 minutes is taken as “b” mm. The compressive recovery isdefined to be b/a. Each thickness is measured in this manner. The term“thickness” as used herein means an average thickness as measured with alaser displacement meter (PA-1830 (trade name), supplied from KeyenceCo., Ltd.) in a usual manner.

The cushioning material can be disposed in the upper portion, the lowerportion or the inside of the absorbent member. It can be disposed in aplurality of positions. In this particular embodiment, the cushioningmaterial is placed under the absorbent member as shown in FIGS. 2 to 4.

While an uneven sheet is used as a cushioning material in thisembodiment as shown in FIGS. 2 to 4, an elastic foamed body, such asurethane foam, expanded polyethylene or skeleton foam, is also useful.In addition, film having elasticity or fiber aggregates havingelasticity such as nonwoven fabric, woven fabric or knitted fabric,comprising natural rubber or thermoplastic elastomers of styrene,urethane, olefin, ester or metallocene-catalyzed ultra-low-densitypolyethylene, and the like can also be used. Especially suitable of themare a urethane foam sheet, and a film or fiber aggregate of an esterelastomer or metalocene-catalyzed ultra-low-density polyethylene.

The uneven sheet includes sheets obtained by forming unevenness on theabove-described film or fiber aggregate having elasticity by such meansas embossing using matched steel rolls. The following uneven sheets 1and 2 can be mentioned as specific examples.

Uneven sheet 1: A 2.0 mm thick uneven sheet having compressive recoveryproperties, which is obtained by embossing a film of ultra-low-densitypolyethylene (basis weight: 60 g/m²; prepared by polymerization using ametallocene catalyst) through matched steel embossing rolls.

Uneven sheet 2: A 2.2 mm thick uneven nonwoven fabric sheet havingcompressive recovery properties, which is obtained by mixing 30% byweight of polyethylene terephthalate (PET)/low-melting elastic PETconjugate fiber (3 denier×51 mm) and 70% by weight of PET fiber (3denier×51 mm), making a fiber web having a basis weight of 50 g/m² fromthe mixed fiber, and embossing the web through matched steel embossingrolls.

The absorbent member can be made up mainly of an absorbent polymer, afiber aggregate, and supporting paper in which the former two arewrapped. In the fourth embodiment, bulky nonwoven fabric as a fiberaggregate which holds an absorbent polymer in the fiber intersticesthereof is wrapped in supporting paper, and the above-mentioned unevensheet is disposed thereunder to make the absorbent member.

The absorbent polymer, fiber aggregate and supporting paper to be usedcan be the same as those used in the first to third embodiments. Inparticular it is preferred to use as an absorbent polymer a combinationof the superabsorbent polymers A and B as used in the third invention inthe specific ratio, which is preferred for retaining high absorbingperformance even where the fluff pulp content is greatly reduced to 30%by weight or less as compared with ordinary diapers as described aboveto make a package of diapers compact. Depending on the kind and amountof the absorbent polymers, fluff pulp may be omitted.

The materials forming each constituent member of the disposable diapersaccording to the first to fourth embodiments are described hereunder.The topsheet, backsheet, water repellent nonwoven fabric and outernonwoven fabric layer can be of any materials generally employed indisposable diapers without particular restriction.

The elastic members for the leg portions, upstanding gathers and waistportions can be of any materials generally used in disposable diaperswith no particular restriction.

Materials for forming the fastening tapes include tape coated with anadhesive and a male member of mechanical fastener. As the landing tape,tape having a release finish, which is combined with tape coated with anadhesive as a fastening tape, and a female member of a generalmechanical fastener, which is combined with a male member, can be usedwith no particular limitation.

Constituted as described above, the disposable diaper of the thirdembodiment is light and compact. Where a plurality of the disposablediapers are packed in a packaging bag as stacked and compressed, theyare light and compact and therefore easy to carry. Moreover, they havehigh leakproofness, effectively preventing leakage of urine either incase where urine rushes out or in case where much urine is dischargedover a long time.

Constituted as described above, the disposable diaper of the fourthembodiment can be made thinner and more compact when packaged. Uponbeing taken out of the package, the diaper restores its thicknessmoderately so that it can be used at ease without giving a user, etc.feelings of unease about the thinness.

While the above embodiments of the practice have been described withparticular reference to unfolded type disposable diapers intended forbabies, the first to third invention are also applicable to pants typedisposable diapers intended for babies and unfolded or pants typedisposable diaper for adults.

The fourth invention is applicable to sanitary napkins, incontinencepads, etc. as well as unfolded or pants type disposable diapers.

The absorbent member used in the third embodiment is suitable as, otherthan the absorbent member of disposable diapers, the absorbent member ofabsorbent articles used for absorbing body fluids, such as sanitarynapkins, incontinence pads and panty liners. In addition, it is usableas the absorbent member of drip sheets, kitchen paper towels, householdcleaning sheets, undersheets for pet animals and the like.

Particulars that have been described with respect to a certainembodiment could apply to other embodiments. Therefore particulars of anembodiment that have not been described above could be understood fromthe corresponding description of other embodiments. The particulars ofthe embodiments are exchangeable among them.

The present invention will now be illustrated in greater detail by wayof Examples, but it should be understood that the present invention isnot construed as being limited thereto.

EXAMPLE 1

A superabsorbent polymer A having a rate of absorption of 11.8 g/30sec/0.3 g by the DW method (10SH-P (trade name), available from SumitomoSeika Chemicals Co., Ltd.) and a superabsorbent polymer B having a rateof absorption of 3.6 g/30 sec/0.3 g by the DW method (CA-W4 (tradename), available from Nippon Shokubai Co., Ltd.) were mixed at a polymerA/polymer B weight ratio of 50/50 to prepare a mixed superabsorbentpolymer. PP/PE core/sheath conjugate fiber and PET fiber were mixed at aweight ratio of 70/30 and fabricated into airthrough nonwoven fabrichaving a basis weight of 30 g/m². The mixed superabsorbent polymer wasscattered on the nonwoven fabric in an amount of 200 g/m² to be held inthe interstices of the fibers. A tissue having a basis weight of 15 g/m²was wrapped about the nonwoven fabric having the polymers held thereinto make an absorbent member.

A PP/PE nonwoven fabric was put on one side of the absorbent member as atopsheet, and on the other side was put a PE film as a backsheet. Knownfastening tapes, waist elastic members, leg elastic members, and thelike were provided to obtain a medium size disposable diaper for babieshaving the form shown in FIG. 1.

EXAMPLE 2

A hot-melt adhesive was applied to a tissue, and the mixedsuperabsorbent polymer prepared in the same manner as in Example 1 wasscattered thereon in an amount of 200 g/m². Another tissue having ahot-melt adhesive applied thereto was superposed thereon to make anabsorbent member. A disposable diaper was obtained by using theresulting absorbent member in the same manner as in Example 1.

COMPARATIVE EXAMPLE 1

A superabsorbent polymer having a rate of absorption of 3.6 g/30 sec/0.3g by the DW method (CA-W4 (trade name), supplied from Nippon Shokubai)and fluff pulp were mixed at a polymer/pulp weight ratio of 40/60 andbuilt up into a sheet having 200 g/m² of the superabsorbent polymer and300 g/m² of the fluff pulp. A tissue having a basis weight 15 g/m² waswrapped about the sheet to make an absorbent member.

A disposable diaper was obtained by using the resulting absorbent memberin the same manner as in Example 1.

COMPARATIVE EXAMPLE 2

The same superabsorbent polymer as used in Comparative Example 1 andfluff pulp were mixed at the same mixing ratio as in Comparative Example1, and the mixture was built up into a sheet having 80 g/m² of thesuperabsorbent polymer and 120 g/m² of the fluff pulp. A tissue having abasis weight of 15 g/m² was wrapped about the sheet to make an absorbentmember.

A disposable diaper was obtained by using the resulting absorbent memberin the same manner as in Example 1.

The weight, product basis weight, rate of absorption and saturatedabsorption of the disposable diapers obtained in Examples 1 and 2 andComparative Examples 1 and 2 were measured. The results obtained areshown in Table 1 below.

In every disposable diaper tested, the test piece taken from theurination point portion, which corresponds to the urination point of awearer, displayed the highest rate of absorption and the highestsaturated absorption of all the test pieces. Therefore, the rate ofabsorption and the saturated absorption shown in Table 1 are those ofthe test piece taken from the urination point portion.

Further, the product basis weight, rate of absorption, and saturatedabsorption of the crotch portion of each disposable diaper were measuredin accordance with the aforementioned methods. In Table 2 are shown theresults of measurement together with the weight of the whole diaper.

The absorbing performance (the maximum absorption) of each disposablediaper was evaluated as follows. The disposable diaper was cut at 225 mmwide of the edge of the front waist portion to make a test piece. Thetest piece was put on a slant mount having an incline of 45° with theedge of the waist portion down as shown in FIG. 6. Portions ofphysiological saline each measuring 40 ml were poured into a position165 mm from the edge of the waist portion at a rate of 5 ml/sec each at5 minute intervals. The maximum amount of physiological saline thatcould be retained by the absorbent member is shown in Tables 1 and 2.The fluff pulp content (wt%) in the disposable diapers of Examples 1 and2 and Comparative Examples 1 and 2 were 0%, 0%, 57%, and 52%,respectively.

TABLE 1 Diaper Basis Saturated Maximum Weight Weight AbsorptionAbsorption Absorption (g) (g/m²) Rate (g/sec) (g/100 cm²) (g) Example 125 192 3.7 100 160 Example 2 24 185 3.2 94 160 Compara. 40 308 3.5 98160 Example 1 Compara. 24 185 2.6 41 80 Example 2

TABLE 2 Basis Weight of Diaper Crotch Saturated Maximum Weight PortionAbsorption Absorption Absorption (g) (g/m²) Rate (g/sec) (g/100 cm²) (g)Example 1 25 340 3.7 100 160 Example 2 24 316 3.2 94 160 Compara. 40 6103.5 98 160 Example 1 Compara. 24 310 2.6 41 80 Example 2

The disposable diapers of Examples 1 and 2, which belong to the firstand the second inventions, weigh 25 g or less each, being significantlylighter than conventional diapers and nevertheless maintain highleakproof performance. Although the disposable diaper of ComparativeExample 1 has high leakproof performance, it is heavy and inconvenientto carry when a plurality of the disposable diapers are combined in apackage. The disposable diaper of Comparative Example 2 corresponds tothat of Comparative Example 1 from which the fluff pulp and thesuperabsorbent polymner making up the absorbent member are cut down by60%. It is light but inferior in resistance to leakage.

EXAMPLE 3

The superabsorbent polymers A and B used in Example 1 were mixed at apolymer A/polymer B weight ratio of 30/70 to prepare a mixedsuperabsorbent polymer.

The mixed superabsorbent polymer, fluff pulp and heat-fusible PP/PEcore/sheath conjugate fiber were mixed up at a weight ratio of 85/10/5and built up into a sheeting having 200 g/m² of the mixed superabsorbentpolymer, 24 g/m² of fluff pulp, and 12 g/m² of the heat-fusibleconjugate fiber. The resulting fiber aggregate was wrapped in a tissuehaving a basis weight of 15 g/m² and subjected to a heat treatment tomake an absorbent member having a fluff content of 9% by weight.

A medium size disposable diaper for babies having the form of FIG. 1 wasprepared in the same manner as in Example 1, except for using the aboveprepared absorbent member.

EXAMPLE 4

The superabsorbent polymers A and B used in Example 3 were mixed at apolymer A/polymer B weight ratio of 50/50 to prepare a mixedsuperabsorbent polymer. The resulting mixed superabsorbent polymer wasscattered on a tissue having a hot-melt adhesive applied thereto in anamount of 200 g/m², and a fluff pulp web having a basis weight of 80g/m² was put thereon. A tissue having a hot-melt adhesive applied wassuperposed on the fluff pulp web to make an absorbent member. The fluffpulp content of the absorbent member was 26% by weight. A disposablediaper was prepared in the same manner as in Example 3, except for usingthe resulting absorbent member.

The following measurement was made on the disposable diapers prepared inExamples 3 and 4. The weight and the product basis weight of the diaperitself were measured in accordance with the methods described in regardto the first embodiment. Rate of body fluid absorption and saturatedbody fluid absorption of the crotch portion were measured according tothe methods described with regard to the second embodiment.

The absorbing performance of the disposable diapers of Examples 3 and 4was evaluated in terms of maximum absorption in accordance with themethod shown in FIG. 6.

The results of these measurements are shown in Table 3 below.

TABLE 3 Diaper Basis Saturated Maximum Weight Weight AbsorptionAbsorption Absorption (g) (g/m²) Rate (g/sec) (g/100 cm²) (g) Example 325 192 3.7 100 160 Example 4 28 215 3.8 102 160 Compara. 40 308 3.5 98160 Example 1 Compara. 24 185 2.6 41 80 Example 2

The disposable diapers of Examples 3 and 4, which belong to the thirdinvention, weigh less than 30 g each, being significantly lighter thanconventional diapers and yet maintain high leakproof performance.Although the disposable diaper of Comparative Example 1 has highleakproof performance owing to the high fluff pulp content in itsabsorbent member, it is heavy and inconvenient to carry when a pluralityof the disposable diapers are combined in a package. The disposablediaper of Comparative Example 2 corresponds to that of ComparativeExample 1 from which the fluff pulp and the superabsorbent polymermaking up the absorbent member are cut down by 60%. It is light butinferior in resistance to leakage.

The high leakproof performance of the disposable diapers according tothe third invention (Examples 3 and 4) for their lightness is consideredto owe to the superabsorbent polymer having a rate of absorption of 8g/30 sec/0.3 g or more by the DW method which carries out the functionconventionally performed by fluff pulp in quickly taking dischargedurine into the inside of the absorbent member.

EXAMPLE 5

Disposable diapers having the form shown in FIG. 1 were fabricated fromknown members, except for using cushioning materials whose thickness andcompressive recovery are shown in Table 4. The thickness under load andno-load thickness of the resulting diapers were measured. The resultsobtained are shown in Table 4.

TABLE 4 Cushioning Material Diaper Thickness* Compressive Thicknessunder No-load Thickness Sample No. Kind (mm) Recovery (%) Load (mm)Thickness (mm) Ratio 1 uneven 2.0 86 2.5 4.2 1.68 sheet 1 2 uneven 2.283 2.8 4.6 1.64 sheet 2 3 urethane 2.3 99 3.0 5.3 1.77 foam 4 skeleton2.5 98 3.2 5.6 1.75 foam Note: *Initial thickness with no load applied.

Industrial Applicability

The first to third inventions provide disposable diapers which are lightand compact and therefore convenient to carry around even when aplurality of the diapers are put in a package and also which areexcellent in leakproofness.

The fourth invention provides absorbent articles, such as disposablediapers, which are compact in a package but restore thickness when takenout of the package to make a user feel at ease while in use. Further,the absorbent articles of the fourth invention have cushioning toprovide a good fit to a wearer on being put on.

This application claims the priority of Japanese Patent Application Nos.11-104626, 11-104627, 11-104628 each filed Apr. 12, 1999 and JapanesePatent Application No. 11-134310 filed May 14, 1999, which areincorporated herein by reference.

What is claimed is:
 1. A disposable diaper comprising a liquid permeabletopsheet, a liquid impermeable backsheet, and a liquid retentiveabsorbent member interposed between said topsheet and said backsheet,wherein said disposable diaper has a product basis weight of 50 to 220g/m², and a portion of said disposable diaper where said absorbentmember is disposed has a part having a rate of body fluid absorption of3.0 g/sec or more and a part having a saturated body fluid absorption of75 g/100 cm² or more.
 2. A disposable diaper according to claim 1,wherein said absorbent member urination point portion corresponds to theurination point of a wearer.
 3. A disposable diaper according to claim1, wherein said absorbent member has a fluff pulp content of 0 to 30% byweight.
 4. A disposable diaper comprising a liquid permeable topsheet, aliquid impermeable backsheet, and a liquid retentive absorbent memberinterposed between said topsheet and said backsheet, wherein saiddisposable diaper has a crotch portion, and said crotch portion has acrotch basis weight of 100 to 450 g/m², a rate of body fluid absorptionof 3.0 g/sec or more, and a saturated body fluid absorption of 60 g/100cm² or more.
 5. A disposable diaper according to claim 4, wherein saidabsorbent member has a fluff pulp content of 0 to 30% by weight.